Chromosomal constitution is altered in a majority of human malignancies and, in some, the cytogenetic changes are specific for the particular tumor type. The objectives of this research are to characterize cystogenetically tropical hepatocellular carcinoma in Nigeria, to investigate the evolution of chromosomal changes from the stage of mere dysplasia to the stage of frank malignancy, to correlate the cytogenetic character of malignant cells to the production of alpha-fetoprotein and the presence or absence of hepatitis B surface antigens. Since the incidence of hepatocellular carcinoma in Central Nigeria is extremely high, the common specific etiologic agent is suggested. Detection of a specific chromosomal marker or rearrangement would reflect the common etiologic factor and will be utilized in early diagnosis and prognosis of the disease.